mm/hmm.c

   1 /*
   2  * Copyright 2013 Red Hat Inc.
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * Authors: JÃ©rÃ´me Glisse <jglisse@redhat.com>
  15  */
  16 /*
  17  * Refer to include/linux/hmm.h for information about heterogeneous memory
  18  * management or HMM for short.
  19  */
  20 #include <linux/mm.h>
  21 #include <linux/hmm.h>
  22 #include <linux/init.h>
  23 #include <linux/rmap.h>
  24 #include <linux/swap.h>
  25 #include <linux/slab.h>
  26 #include <linux/sched.h>
  27 #include <linux/mmzone.h>
  28 #include <linux/pagemap.h>
  29 #include <linux/swapops.h>
  30 #include <linux/hugetlb.h>
  31 #include <linux/memremap.h>
  32 #include <linux/jump_label.h>
  33 #include <linux/mmu_notifier.h>
  34 #include <linux/memory_hotplug.h>
  35
  36 #define PA_SECTION_SIZE (1UL << PA_SECTION_SHIFT)
  37
  38 #if defined(CONFIG_DEVICE_PRIVATE) || defined(CONFIG_DEVICE_PUBLIC)
  39 /*
  40  * Device private memory see HMM (Documentation/vm/hmm.txt) or hmm.h
  41  */
  42 DEFINE_STATIC_KEY_FALSE(device_private_key);
  43 EXPORT_SYMBOL(device_private_key);
  44 #endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
  45
  46
  47 #if IS_ENABLED(CONFIG_HMM_MIRROR)
  48 static const struct mmu_notifier_ops hmm_mmu_notifier_ops;
  49
  50 /*
  51  * struct hmm - HMM per mm struct
  52  *
  53  * @mm: mm struct this HMM struct is bound to
  54  * @lock: lock protecting ranges list
  55  * @sequence: we track updates to the CPU page table with a sequence number
  56  * @ranges: list of range being snapshotted
  57  * @mirrors: list of mirrors for this mm
  58  * @mmu_notifier: mmu notifier to track updates to CPU page table
  59  * @mirrors_sem: read/write semaphore protecting the mirrors list
  60  */
  61 struct hmm {
  62         struct mm_struct        *mm;
  63         spinlock_t              lock;
  64         atomic_t                sequence;
  65         struct list_head        ranges;
  66         struct list_head        mirrors;
  67         struct mmu_notifier     mmu_notifier;
  68         struct rw_semaphore     mirrors_sem;
  69 };
  70
  71 /*
  72  * hmm_register - register HMM against an mm (HMM internal)
  73  *
  74  * @mm: mm struct to attach to
  75  *
  76  * This is not intended to be used directly by device drivers. It allocates an
  77  * HMM struct if mm does not have one, and initializes it.
  78  */
  79 static struct hmm *hmm_register(struct mm_struct *mm)
  80 {
  81         struct hmm *hmm = READ_ONCE(mm->hmm);
  82         bool cleanup = false;
  83
  84         /*
  85          * The hmm struct can only be freed once the mm_struct goes away,
  86          * hence we should always have pre-allocated an new hmm struct
  87          * above.
  88          */
  89         if (hmm)
  90                 return hmm;
  91
  92         hmm = kmalloc(sizeof(*hmm), GFP_KERNEL);
  93         if (!hmm)
  94                 return NULL;
  95         INIT_LIST_HEAD(&hmm->mirrors);
  96         init_rwsem(&hmm->mirrors_sem);
  97         atomic_set(&hmm->sequence, 0);
  98         hmm->mmu_notifier.ops = NULL;
  99         INIT_LIST_HEAD(&hmm->ranges);
 100         spin_lock_init(&hmm->lock);
 101         hmm->mm = mm;
 102
 103         /*
 104          * We should only get here if hold the mmap_sem in write mode ie on
 105          * registration of first mirror through hmm_mirror_register()
 106          */
 107         hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops;
 108         if (__mmu_notifier_register(&hmm->mmu_notifier, mm)) {
 109                 kfree(hmm);
 110                 return NULL;
 111         }
 112
 113         spin_lock(&mm->page_table_lock);
 114         if (!mm->hmm)
 115                 mm->hmm = hmm;
 116         else
 117                 cleanup = true;
 118         spin_unlock(&mm->page_table_lock);
 119
 120         if (cleanup) {
 121                 mmu_notifier_unregister(&hmm->mmu_notifier, mm);
 122                 kfree(hmm);
 123         }
 124
 125         return mm->hmm;
 126 }
 127
 128 void hmm_mm_destroy(struct mm_struct *mm)
 129 {
 130         kfree(mm->hmm);
 131 }
 132
 133 static void hmm_invalidate_range(struct hmm *hmm,
 134                                  enum hmm_update_type action,
 135                                  unsigned long start,
 136                                  unsigned long end)
 137 {
 138         struct hmm_mirror *mirror;
 139         struct hmm_range *range;
 140
 141         spin_lock(&hmm->lock);
 142         list_for_each_entry(range, &hmm->ranges, list) {
 143                 unsigned long addr, idx, npages;
 144
 145                 if (end < range->start || start >= range->end)
 146                         continue;
 147
 148                 range->valid = false;
 149                 addr = max(start, range->start);
 150                 idx = (addr - range->start) >> PAGE_SHIFT;
 151                 npages = (min(range->end, end) - addr) >> PAGE_SHIFT;
 152                 memset(&range->pfns[idx], 0, sizeof(*range->pfns) * npages);
 153         }
 154         spin_unlock(&hmm->lock);
 155
 156         down_read(&hmm->mirrors_sem);
 157         list_for_each_entry(mirror, &hmm->mirrors, list)
 158                 mirror->ops->sync_cpu_device_pagetables(mirror, action,
 159                                                         start, end);
 160         up_read(&hmm->mirrors_sem);
 161 }
 162
 163 static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm)
 164 {
 165         struct hmm_mirror *mirror;
 166         struct hmm *hmm = mm->hmm;
 167
 168         down_write(&hmm->mirrors_sem);
 169         mirror = list_first_entry_or_null(&hmm->mirrors, struct hmm_mirror,
 170                                           list);
 171         while (mirror) {
 172                 list_del_init(&mirror->list);
 173                 if (mirror->ops->release) {
 174                         /*
 175                          * Drop mirrors_sem so callback can wait on any pending
 176                          * work that might itself trigger mmu_notifier callback
 177                          * and thus would deadlock with us.
 178                          */
 179                         up_write(&hmm->mirrors_sem);
 180                         mirror->ops->release(mirror);
 181                         down_write(&hmm->mirrors_sem);
 182                 }
 183                 mirror = list_first_entry_or_null(&hmm->mirrors,
 184                                                   struct hmm_mirror, list);
 185         }
 186         up_write(&hmm->mirrors_sem);
 187 }
 188
 189 static void hmm_invalidate_range_start(struct mmu_notifier *mn,
 190                                        struct mm_struct *mm,
 191                                        unsigned long start,
 192                                        unsigned long end)
 193 {
 194         struct hmm *hmm = mm->hmm;
 195
 196         VM_BUG_ON(!hmm);
 197
 198         atomic_inc(&hmm->sequence);
 199 }
 200
 201 static void hmm_invalidate_range_end(struct mmu_notifier *mn,
 202                                      struct mm_struct *mm,
 203                                      unsigned long start,
 204                                      unsigned long end)
 205 {
 206         struct hmm *hmm = mm->hmm;
 207
 208         VM_BUG_ON(!hmm);
 209
 210         hmm_invalidate_range(mm->hmm, HMM_UPDATE_INVALIDATE, start, end);
 211 }
 212
 213 static const struct mmu_notifier_ops hmm_mmu_notifier_ops = {
 214         .release                = hmm_release,
 215         .invalidate_range_start = hmm_invalidate_range_start,
 216         .invalidate_range_end   = hmm_invalidate_range_end,
 217 };
 218
 219 /*
 220  * hmm_mirror_register() - register a mirror against an mm
 221  *
 222  * @mirror: new mirror struct to register
 223  * @mm: mm to register against
 224  *
 225  * To start mirroring a process address space, the device driver must register
 226  * an HMM mirror struct.
 227  *
 228  * THE mm->mmap_sem MUST BE HELD IN WRITE MODE !
 229  */
 230 int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm)
 231 {
 232         /* Sanity check */
 233         if (!mm || !mirror || !mirror->ops)
 234                 return -EINVAL;
 235
 236 again:
 237         mirror->hmm = hmm_register(mm);
 238         if (!mirror->hmm)
 239                 return -ENOMEM;
 240
 241         down_write(&mirror->hmm->mirrors_sem);
 242         if (mirror->hmm->mm == NULL) {
 243                 /*
 244                  * A racing hmm_mirror_unregister() is about to destroy the hmm
 245                  * struct. Try again to allocate a new one.
 246                  */
 247                 up_write(&mirror->hmm->mirrors_sem);
 248                 mirror->hmm = NULL;
 249                 goto again;
 250         } else {
 251                 list_add(&mirror->list, &mirror->hmm->mirrors);
 252                 up_write(&mirror->hmm->mirrors_sem);
 253         }
 254
 255         return 0;
 256 }
 257 EXPORT_SYMBOL(hmm_mirror_register);
 258
 259 /*
 260  * hmm_mirror_unregister() - unregister a mirror
 261  *
 262  * @mirror: new mirror struct to register
 263  *
 264  * Stop mirroring a process address space, and cleanup.
 265  */
 266 void hmm_mirror_unregister(struct hmm_mirror *mirror)
 267 {
 268         bool should_unregister = false;
 269         struct mm_struct *mm;
 270         struct hmm *hmm;
 271
 272         if (mirror->hmm == NULL)
 273                 return;
 274
 275         hmm = mirror->hmm;
 276         down_write(&hmm->mirrors_sem);
 277         list_del_init(&mirror->list);
 278         should_unregister = list_empty(&hmm->mirrors);
 279         mirror->hmm = NULL;
 280         mm = hmm->mm;
 281         hmm->mm = NULL;
 282         up_write(&hmm->mirrors_sem);
 283
 284         if (!should_unregister || mm == NULL)
 285                 return;
 286
 287         spin_lock(&mm->page_table_lock);
 288         if (mm->hmm == hmm)
 289                 mm->hmm = NULL;
 290         spin_unlock(&mm->page_table_lock);
 291
 292         mmu_notifier_unregister_no_release(&hmm->mmu_notifier, mm);
 293         kfree(hmm);
 294 }
 295 EXPORT_SYMBOL(hmm_mirror_unregister);
 296
 297 struct hmm_vma_walk {
 298         struct hmm_range        *range;
 299         unsigned long           last;
 300         bool                    fault;
 301         bool                    block;
 302         bool                    write;
 303 };
 304
 305 static int hmm_vma_do_fault(struct mm_walk *walk,
 306                             unsigned long addr,
 307                             uint64_t *pfn)
 308 {
 309         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_REMOTE;
 310         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 311         struct vm_area_struct *vma = walk->vma;
 312         int r;
 313
 314         flags |= hmm_vma_walk->block ? 0 : FAULT_FLAG_ALLOW_RETRY;
 315         flags |= hmm_vma_walk->write ? FAULT_FLAG_WRITE : 0;
 316         r = handle_mm_fault(vma, addr, flags);
 317         if (r & VM_FAULT_RETRY)
 318                 return -EBUSY;
 319         if (r & VM_FAULT_ERROR) {
 320                 *pfn = HMM_PFN_ERROR;
 321                 return -EFAULT;
 322         }
 323
 324         return -EAGAIN;
 325 }
 326
 327 static int hmm_pfns_bad(unsigned long addr,
 328                         unsigned long end,
 329                         struct mm_walk *walk)
 330 {
 331         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 332         struct hmm_range *range = hmm_vma_walk->range;
 333         uint64_t *pfns = range->pfns;
 334         unsigned long i;
 335
 336         i = (addr - range->start) >> PAGE_SHIFT;
 337         for (; addr < end; addr += PAGE_SIZE, i++)
 338                 pfns[i] = HMM_PFN_ERROR;
 339
 340         return 0;
 341 }
 342
 343 static void hmm_pfns_clear(uint64_t *pfns,
 344                            unsigned long addr,
 345                            unsigned long end)
 346 {
 347         for (; addr < end; addr += PAGE_SIZE, pfns++)
 348                 *pfns = 0;
 349 }
 350
 351 /*
 352  * hmm_vma_walk_hole() - handle a range lacking valid pmd or pte(s)
 353  * @start: range virtual start address (inclusive)
 354  * @end: range virtual end address (exclusive)
 355  * @walk: mm_walk structure
 356  * Returns: 0 on success, -EAGAIN after page fault, or page fault error
 357  *
 358  * This function will be called whenever pmd_none() or pte_none() returns true,
 359  * or whenever there is no page directory covering the virtual address range.
 360  */
 361 static int hmm_vma_walk_hole(unsigned long addr,
 362                              unsigned long end,
 363                              struct mm_walk *walk)
 364 {
 365         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 366         struct hmm_range *range = hmm_vma_walk->range;
 367         uint64_t *pfns = range->pfns;
 368         unsigned long i;
 369
 370         hmm_vma_walk->last = addr;
 371         i = (addr - range->start) >> PAGE_SHIFT;
 372         for (; addr < end; addr += PAGE_SIZE, i++) {
 373                 pfns[i] = 0;
 374                 if (hmm_vma_walk->fault) {
 375                         int ret;
 376
 377                         ret = hmm_vma_do_fault(walk, addr, &pfns[i]);
 378                         if (ret != -EAGAIN)
 379                                 return ret;
 380                 }
 381         }
 382
 383         return hmm_vma_walk->fault ? -EAGAIN : 0;
 384 }
 385
 386 static int hmm_vma_walk_pmd(pmd_t *pmdp,
 387                             unsigned long start,
 388                             unsigned long end,
 389                             struct mm_walk *walk)
 390 {
 391         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 392         struct hmm_range *range = hmm_vma_walk->range;
 393         struct vm_area_struct *vma = walk->vma;
 394         uint64_t *pfns = range->pfns;
 395         unsigned long addr = start, i;
 396         bool write_fault;
 397         pte_t *ptep;
 398
 399         i = (addr - range->start) >> PAGE_SHIFT;
 400         write_fault = hmm_vma_walk->fault & hmm_vma_walk->write;
 401
 402 again:
 403         if (pmd_none(*pmdp))
 404                 return hmm_vma_walk_hole(start, end, walk);
 405
 406         if (pmd_huge(*pmdp) && vma->vm_flags & VM_HUGETLB)
 407                 return hmm_pfns_bad(start, end, walk);
 408
 409         if (pmd_devmap(*pmdp) || pmd_trans_huge(*pmdp)) {
 410                 unsigned long pfn;
 411                 uint64_t flag = 0;
 412                 pmd_t pmd;
 413
 414                 /*
 415                  * No need to take pmd_lock here, even if some other threads
 416                  * is splitting the huge pmd we will get that event through
 417                  * mmu_notifier callback.
 418                  *
 419                  * So just read pmd value and check again its a transparent
 420                  * huge or device mapping one and compute corresponding pfn
 421                  * values.
 422                  */
 423                 pmd = pmd_read_atomic(pmdp);
 424                 barrier();
 425                 if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
 426                         goto again;
 427                 if (pmd_protnone(pmd))
 428                         return hmm_vma_walk_hole(start, end, walk);
 429
 430                 if (write_fault && !pmd_write(pmd))
 431                         return hmm_vma_walk_hole(start, end, walk);
 432
 433                 pfn = pmd_pfn(pmd) + pte_index(addr);
 434                 flag |= pmd_write(pmd) ? HMM_PFN_WRITE : 0;
 435                 for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
 436                         pfns[i] = hmm_pfn_from_pfn(pfn) | flag;
 437                 return 0;
 438         }
 439
 440         if (pmd_bad(*pmdp))
 441                 return hmm_pfns_bad(start, end, walk);
 442
 443         ptep = pte_offset_map(pmdp, addr);
 444         for (; addr < end; addr += PAGE_SIZE, ptep++, i++) {
 445                 pte_t pte = *ptep;
 446
 447                 pfns[i] = 0;
 448
 449                 if (pte_none(pte)) {
 450                         pfns[i] = 0;
 451                         if (hmm_vma_walk->fault)
 452                                 goto fault;
 453                         continue;
 454                 }
 455
 456                 if (!pte_present(pte)) {
 457                         swp_entry_t entry = pte_to_swp_entry(pte);
 458
 459                         if (!non_swap_entry(entry)) {
 460                                 if (hmm_vma_walk->fault)
 461                                         goto fault;
 462                                 continue;
 463                         }
 464
 465                         /*
 466                          * This is a special swap entry, ignore migration, use
 467                          * device and report anything else as error.
 468                          */
 469                         if (is_device_private_entry(entry)) {
 470                                 pfns[i] = hmm_pfn_from_pfn(swp_offset(entry));
 471                                 if (is_write_device_private_entry(entry)) {
 472                                         pfns[i] |= HMM_PFN_WRITE;
 473                                 } else if (write_fault)
 474                                         goto fault;
 475                                 pfns[i] |= HMM_PFN_DEVICE_UNADDRESSABLE;
 476                         } else if (is_migration_entry(entry)) {
 477                                 if (hmm_vma_walk->fault) {
 478                                         pte_unmap(ptep);
 479                                         hmm_vma_walk->last = addr;
 480                                         migration_entry_wait(vma->vm_mm,
 481                                                              pmdp, addr);
 482                                         return -EAGAIN;
 483                                 }
 484                                 continue;
 485                         } else {
 486                                 /* Report error for everything else */
 487                                 pfns[i] = HMM_PFN_ERROR;
 488                         }
 489                         continue;
 490                 }
 491
 492                 if (write_fault && !pte_write(pte))
 493                         goto fault;
 494
 495                 pfns[i] = hmm_pfn_from_pfn(pte_pfn(pte));
 496                 pfns[i] |= pte_write(pte) ? HMM_PFN_WRITE : 0;
 497                 continue;
 498
 499 fault:
 500                 pte_unmap(ptep);
 501                 /* Fault any virtual address we were asked to fault */
 502                 return hmm_vma_walk_hole(start, end, walk);
 503         }
 504         pte_unmap(ptep - 1);
 505
 506         return 0;
 507 }
 508
 509 static void hmm_pfns_special(struct hmm_range *range)
 510 {
 511         unsigned long addr = range->start, i = 0;
 512
 513         for (; addr < range->end; addr += PAGE_SIZE, i++)
 514                 range->pfns[i] = HMM_PFN_SPECIAL;
 515 }
 516
 517 /*
 518  * hmm_vma_get_pfns() - snapshot CPU page table for a range of virtual addresses
 519  * @range: range being snapshotted
 520  * Returns: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid
 521  *          vma permission, 0 success
 522  *
 523  * This snapshots the CPU page table for a range of virtual addresses. Snapshot
 524  * validity is tracked by range struct. See hmm_vma_range_done() for further
 525  * information.
 526  *
 527  * The range struct is initialized here. It tracks the CPU page table, but only
 528  * if the function returns success (0), in which case the caller must then call
 529  * hmm_vma_range_done() to stop CPU page table update tracking on this range.
 530  *
 531  * NOT CALLING hmm_vma_range_done() IF FUNCTION RETURNS 0 WILL LEAD TO SERIOUS
 532  * MEMORY CORRUPTION ! YOU HAVE BEEN WARNED !
 533  */
 534 int hmm_vma_get_pfns(struct hmm_range *range)
 535 {
 536         struct vm_area_struct *vma = range->vma;
 537         struct hmm_vma_walk hmm_vma_walk;
 538         struct mm_walk mm_walk;
 539         struct hmm *hmm;
 540
 541         /* Sanity check, this really should not happen ! */
 542         if (range->start < vma->vm_start || range->start >= vma->vm_end)
 543                 return -EINVAL;
 544         if (range->end < vma->vm_start || range->end > vma->vm_end)
 545                 return -EINVAL;
 546
 547         hmm = hmm_register(vma->vm_mm);
 548         if (!hmm)
 549                 return -ENOMEM;
 550         /* Caller must have registered a mirror, via hmm_mirror_register() ! */
 551         if (!hmm->mmu_notifier.ops)
 552                 return -EINVAL;
 553
 554         /* FIXME support hugetlb fs */
 555         if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)) {
 556                 hmm_pfns_special(range);
 557                 return -EINVAL;
 558         }
 559
 560         if (!(vma->vm_flags & VM_READ)) {
 561                 /*
 562                  * If vma do not allow read access, then assume that it does
 563                  * not allow write access, either. Architecture that allow
 564                  * write without read access are not supported by HMM, because
 565                  * operations such has atomic access would not work.
 566                  */
 567                 hmm_pfns_clear(range->pfns, range->start, range->end);
 568                 return -EPERM;
 569         }
 570
 571         /* Initialize range to track CPU page table update */
 572         spin_lock(&hmm->lock);
 573         range->valid = true;
 574         list_add_rcu(&range->list, &hmm->ranges);
 575         spin_unlock(&hmm->lock);
 576
 577         hmm_vma_walk.fault = false;
 578         hmm_vma_walk.range = range;
 579         mm_walk.private = &hmm_vma_walk;
 580
 581         mm_walk.vma = vma;
 582         mm_walk.mm = vma->vm_mm;
 583         mm_walk.pte_entry = NULL;
 584         mm_walk.test_walk = NULL;
 585         mm_walk.hugetlb_entry = NULL;
 586         mm_walk.pmd_entry = hmm_vma_walk_pmd;
 587         mm_walk.pte_hole = hmm_vma_walk_hole;
 588
 589         walk_page_range(range->start, range->end, &mm_walk);
 590         return 0;
 591 }
 592 EXPORT_SYMBOL(hmm_vma_get_pfns);
 593
 594 /*
 595  * hmm_vma_range_done() - stop tracking change to CPU page table over a range
 596  * @range: range being tracked
 597  * Returns: false if range data has been invalidated, true otherwise
 598  *
 599  * Range struct is used to track updates to the CPU page table after a call to
 600  * either hmm_vma_get_pfns() or hmm_vma_fault(). Once the device driver is done
 601  * using the data,  or wants to lock updates to the data it got from those
 602  * functions, it must call the hmm_vma_range_done() function, which will then
 603  * stop tracking CPU page table updates.
 604  *
 605  * Note that device driver must still implement general CPU page table update
 606  * tracking either by using hmm_mirror (see hmm_mirror_register()) or by using
 607  * the mmu_notifier API directly.
 608  *
 609  * CPU page table update tracking done through hmm_range is only temporary and
 610  * to be used while trying to duplicate CPU page table contents for a range of
 611  * virtual addresses.
 612  *
 613  * There are two ways to use this :
 614  * again:
 615  *   hmm_vma_get_pfns(range); or hmm_vma_fault(...);
 616  *   trans = device_build_page_table_update_transaction(pfns);
 617  *   device_page_table_lock();
 618  *   if (!hmm_vma_range_done(range)) {
 619  *     device_page_table_unlock();
 620  *     goto again;
 621  *   }
 622  *   device_commit_transaction(trans);
 623  *   device_page_table_unlock();
 624  *
 625  * Or:
 626  *   hmm_vma_get_pfns(range); or hmm_vma_fault(...);
 627  *   device_page_table_lock();
 628  *   hmm_vma_range_done(range);
 629  *   device_update_page_table(range->pfns);
 630  *   device_page_table_unlock();
 631  */
 632 bool hmm_vma_range_done(struct hmm_range *range)
 633 {
 634         unsigned long npages = (range->end - range->start) >> PAGE_SHIFT;
 635         struct hmm *hmm;
 636
 637         if (range->end <= range->start) {
 638                 BUG();
 639                 return false;
 640         }
 641
 642         hmm = hmm_register(range->vma->vm_mm);
 643         if (!hmm) {
 644                 memset(range->pfns, 0, sizeof(*range->pfns) * npages);
 645                 return false;
 646         }
 647
 648         spin_lock(&hmm->lock);
 649         list_del_rcu(&range->list);
 650         spin_unlock(&hmm->lock);
 651
 652         return range->valid;
 653 }
 654 EXPORT_SYMBOL(hmm_vma_range_done);
 655
 656 /*
 657  * hmm_vma_fault() - try to fault some address in a virtual address range
 658  * @range: range being faulted
 659  * @write: is it a write fault
 660  * @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem)
 661  * Returns: 0 success, error otherwise (-EAGAIN means mmap_sem have been drop)
 662  *
 663  * This is similar to a regular CPU page fault except that it will not trigger
 664  * any memory migration if the memory being faulted is not accessible by CPUs.
 665  *
 666  * On error, for one virtual address in the range, the function will mark the
 667  * corresponding HMM pfn entry with an error flag.
 668  *
 669  * Expected use pattern:
 670  * retry:
 671  *   down_read(&mm->mmap_sem);
 672  *   // Find vma and address device wants to fault, initialize hmm_pfn_t
 673  *   // array accordingly
 674  *   ret = hmm_vma_fault(range, write, block);
 675  *   switch (ret) {
 676  *   case -EAGAIN:
 677  *     hmm_vma_range_done(range);
 678  *     // You might want to rate limit or yield to play nicely, you may
 679  *     // also commit any valid pfn in the array assuming that you are
 680  *     // getting true from hmm_vma_range_monitor_end()
 681  *     goto retry;
 682  *   case 0:
 683  *     break;
 684  *   case -ENOMEM:
 685  *   case -EINVAL:
 686  *   case -EPERM:
 687  *   default:
 688  *     // Handle error !
 689  *     up_read(&mm->mmap_sem)
 690  *     return;
 691  *   }
 692  *   // Take device driver lock that serialize device page table update
 693  *   driver_lock_device_page_table_update();
 694  *   hmm_vma_range_done(range);
 695  *   // Commit pfns we got from hmm_vma_fault()
 696  *   driver_unlock_device_page_table_update();
 697  *   up_read(&mm->mmap_sem)
 698  *
 699  * YOU MUST CALL hmm_vma_range_done() AFTER THIS FUNCTION RETURN SUCCESS (0)
 700  * BEFORE FREEING THE range struct OR YOU WILL HAVE SERIOUS MEMORY CORRUPTION !
 701  *
 702  * YOU HAVE BEEN WARNED !
 703  */
 704 int hmm_vma_fault(struct hmm_range *range, bool write, bool block)
 705 {
 706         struct vm_area_struct *vma = range->vma;
 707         unsigned long start = range->start;
 708         struct hmm_vma_walk hmm_vma_walk;
 709         struct mm_walk mm_walk;
 710         struct hmm *hmm;
 711         int ret;
 712
 713         /* Sanity check, this really should not happen ! */
 714         if (range->start < vma->vm_start || range->start >= vma->vm_end)
 715                 return -EINVAL;
 716         if (range->end < vma->vm_start || range->end > vma->vm_end)
 717                 return -EINVAL;
 718
 719         hmm = hmm_register(vma->vm_mm);
 720         if (!hmm) {
 721                 hmm_pfns_clear(range->pfns, range->start, range->end);
 722                 return -ENOMEM;
 723         }
 724         /* Caller must have registered a mirror using hmm_mirror_register() */
 725         if (!hmm->mmu_notifier.ops)
 726                 return -EINVAL;
 727
 728         /* FIXME support hugetlb fs */
 729         if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)) {
 730                 hmm_pfns_special(range);
 731                 return -EINVAL;
 732         }
 733
 734         if (!(vma->vm_flags & VM_READ)) {
 735                 /*
 736                  * If vma do not allow read access, then assume that it does
 737                  * not allow write access, either. Architecture that allow
 738                  * write without read access are not supported by HMM, because
 739                  * operations such has atomic access would not work.
 740                  */
 741                 hmm_pfns_clear(range->pfns, range->start, range->end);
 742                 return -EPERM;
 743         }
 744
 745         /* Initialize range to track CPU page table update */
 746         spin_lock(&hmm->lock);
 747         range->valid = true;
 748         list_add_rcu(&range->list, &hmm->ranges);
 749         spin_unlock(&hmm->lock);
 750
 751         hmm_vma_walk.fault = true;
 752         hmm_vma_walk.write = write;
 753         hmm_vma_walk.block = block;
 754         hmm_vma_walk.range = range;
 755         mm_walk.private = &hmm_vma_walk;
 756         hmm_vma_walk.last = range->start;
 757
 758         mm_walk.vma = vma;
 759         mm_walk.mm = vma->vm_mm;
 760         mm_walk.pte_entry = NULL;
 761         mm_walk.test_walk = NULL;
 762         mm_walk.hugetlb_entry = NULL;
 763         mm_walk.pmd_entry = hmm_vma_walk_pmd;
 764         mm_walk.pte_hole = hmm_vma_walk_hole;
 765
 766         do {
 767                 ret = walk_page_range(start, range->end, &mm_walk);
 768                 start = hmm_vma_walk.last;
 769         } while (ret == -EAGAIN);
 770
 771         if (ret) {
 772                 unsigned long i;
 773
 774                 i = (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
 775                 hmm_pfns_clear(&range->pfns[i], hmm_vma_walk.last, range->end);
 776                 hmm_vma_range_done(range);
 777         }
 778         return ret;
 779 }
 780 EXPORT_SYMBOL(hmm_vma_fault);
 781 #endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */
 782
 783
 784 #if IS_ENABLED(CONFIG_DEVICE_PRIVATE) ||  IS_ENABLED(CONFIG_DEVICE_PUBLIC)
 785 struct page *hmm_vma_alloc_locked_page(struct vm_area_struct *vma,
 786                                        unsigned long addr)
 787 {
 788         struct page *page;
 789
 790         page = alloc_page_vma(GFP_HIGHUSER, vma, addr);
 791         if (!page)
 792                 return NULL;
 793         lock_page(page);
 794         return page;
 795 }
 796 EXPORT_SYMBOL(hmm_vma_alloc_locked_page);
 797
 798
 799 static void hmm_devmem_ref_release(struct percpu_ref *ref)
 800 {
 801         struct hmm_devmem *devmem;
 802
 803         devmem = container_of(ref, struct hmm_devmem, ref);
 804         complete(&devmem->completion);
 805 }
 806
 807 static void hmm_devmem_ref_exit(void *data)
 808 {
 809         struct percpu_ref *ref = data;
 810         struct hmm_devmem *devmem;
 811
 812         devmem = container_of(ref, struct hmm_devmem, ref);
 813         percpu_ref_exit(ref);
 814         devm_remove_action(devmem->device, &hmm_devmem_ref_exit, data);
 815 }
 816
 817 static void hmm_devmem_ref_kill(void *data)
 818 {
 819         struct percpu_ref *ref = data;
 820         struct hmm_devmem *devmem;
 821
 822         devmem = container_of(ref, struct hmm_devmem, ref);
 823         percpu_ref_kill(ref);
 824         wait_for_completion(&devmem->completion);
 825         devm_remove_action(devmem->device, &hmm_devmem_ref_kill, data);
 826 }
 827
 828 static int hmm_devmem_fault(struct vm_area_struct *vma,
 829                             unsigned long addr,
 830                             const struct page *page,
 831                             unsigned int flags,
 832                             pmd_t *pmdp)
 833 {
 834         struct hmm_devmem *devmem = page->pgmap->data;
 835
 836         return devmem->ops->fault(devmem, vma, addr, page, flags, pmdp);
 837 }
 838
 839 static void hmm_devmem_free(struct page *page, void *data)
 840 {
 841         struct hmm_devmem *devmem = data;
 842
 843         devmem->ops->free(devmem, page);
 844 }
 845
 846 static DEFINE_MUTEX(hmm_devmem_lock);
 847 static RADIX_TREE(hmm_devmem_radix, GFP_KERNEL);
 848
 849 static void hmm_devmem_radix_release(struct resource *resource)
 850 {
 851         resource_size_t key, align_start, align_size;
 852
 853         align_start = resource->start & ~(PA_SECTION_SIZE - 1);
 854         align_size = ALIGN(resource_size(resource), PA_SECTION_SIZE);
 855
 856         mutex_lock(&hmm_devmem_lock);
 857         for (key = resource->start;
 858              key <= resource->end;
 859              key += PA_SECTION_SIZE)
 860                 radix_tree_delete(&hmm_devmem_radix, key >> PA_SECTION_SHIFT);
 861         mutex_unlock(&hmm_devmem_lock);
 862 }
 863
 864 static void hmm_devmem_release(struct device *dev, void *data)
 865 {
 866         struct hmm_devmem *devmem = data;
 867         struct resource *resource = devmem->resource;
 868         unsigned long start_pfn, npages;
 869         struct zone *zone;
 870         struct page *page;
 871
 872         if (percpu_ref_tryget_live(&devmem->ref)) {
 873                 dev_WARN(dev, "%s: page mapping is still live!\n", __func__);
 874                 percpu_ref_put(&devmem->ref);
 875         }
 876
 877         /* pages are dead and unused, undo the arch mapping */
 878         start_pfn = (resource->start & ~(PA_SECTION_SIZE - 1)) >> PAGE_SHIFT;
 879         npages = ALIGN(resource_size(resource), PA_SECTION_SIZE) >> PAGE_SHIFT;
 880
 881         page = pfn_to_page(start_pfn);
 882         zone = page_zone(page);
 883
 884         mem_hotplug_begin();
 885         if (resource->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY)
 886                 __remove_pages(zone, start_pfn, npages, NULL);
 887         else
 888                 arch_remove_memory(start_pfn << PAGE_SHIFT,
 889                                    npages << PAGE_SHIFT, NULL);
 890         mem_hotplug_done();
 891
 892         hmm_devmem_radix_release(resource);
 893 }
 894
 895 static struct hmm_devmem *hmm_devmem_find(resource_size_t phys)
 896 {
 897         WARN_ON_ONCE(!rcu_read_lock_held());
 898
 899         return radix_tree_lookup(&hmm_devmem_radix, phys >> PA_SECTION_SHIFT);
 900 }
 901
 902 static int hmm_devmem_pages_create(struct hmm_devmem *devmem)
 903 {
 904         resource_size_t key, align_start, align_size, align_end;
 905         struct device *device = devmem->device;
 906         int ret, nid, is_ram;
 907         unsigned long pfn;
 908
 909         align_start = devmem->resource->start & ~(PA_SECTION_SIZE - 1);
 910         align_size = ALIGN(devmem->resource->start +
 911                            resource_size(devmem->resource),
 912                            PA_SECTION_SIZE) - align_start;
 913
 914         is_ram = region_intersects(align_start, align_size,
 915                                    IORESOURCE_SYSTEM_RAM,
 916                                    IORES_DESC_NONE);
 917         if (is_ram == REGION_MIXED) {
 918                 WARN_ONCE(1, "%s attempted on mixed region %pr\n",
 919                                 __func__, devmem->resource);
 920                 return -ENXIO;
 921         }
 922         if (is_ram == REGION_INTERSECTS)
 923                 return -ENXIO;
 924
 925         if (devmem->resource->desc == IORES_DESC_DEVICE_PUBLIC_MEMORY)
 926                 devmem->pagemap.type = MEMORY_DEVICE_PUBLIC;
 927         else
 928                 devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
 929
 930         devmem->pagemap.res = *devmem->resource;
 931         devmem->pagemap.page_fault = hmm_devmem_fault;
 932         devmem->pagemap.page_free = hmm_devmem_free;
 933         devmem->pagemap.dev = devmem->device;
 934         devmem->pagemap.ref = &devmem->ref;
 935         devmem->pagemap.data = devmem;
 936
 937         mutex_lock(&hmm_devmem_lock);
 938         align_end = align_start + align_size - 1;
 939         for (key = align_start; key <= align_end; key += PA_SECTION_SIZE) {
 940                 struct hmm_devmem *dup;
 941
 942                 rcu_read_lock();
 943                 dup = hmm_devmem_find(key);
 944                 rcu_read_unlock();
 945                 if (dup) {
 946                         dev_err(device, "%s: collides with mapping for %s\n",
 947                                 __func__, dev_name(dup->device));
 948                         mutex_unlock(&hmm_devmem_lock);
 949                         ret = -EBUSY;
 950                         goto error;
 951                 }
 952                 ret = radix_tree_insert(&hmm_devmem_radix,
 953                                         key >> PA_SECTION_SHIFT,
 954                                         devmem);
 955                 if (ret) {
 956                         dev_err(device, "%s: failed: %d\n", __func__, ret);
 957                         mutex_unlock(&hmm_devmem_lock);
 958                         goto error_radix;
 959                 }
 960         }
 961         mutex_unlock(&hmm_devmem_lock);
 962
 963         nid = dev_to_node(device);
 964         if (nid < 0)
 965                 nid = numa_mem_id();
 966
 967         mem_hotplug_begin();
 968         /*
 969          * For device private memory we call add_pages() as we only need to
 970          * allocate and initialize struct page for the device memory. More-
 971          * over the device memory is un-accessible thus we do not want to
 972          * create a linear mapping for the memory like arch_add_memory()
 973          * would do.
 974          *
 975          * For device public memory, which is accesible by the CPU, we do
 976          * want the linear mapping and thus use arch_add_memory().
 977          */
 978         if (devmem->pagemap.type == MEMORY_DEVICE_PUBLIC)
 979                 ret = arch_add_memory(nid, align_start, align_size, NULL,
 980                                 false);
 981         else
 982                 ret = add_pages(nid, align_start >> PAGE_SHIFT,
 983                                 align_size >> PAGE_SHIFT, NULL, false);
 984         if (ret) {
 985                 mem_hotplug_done();
 986                 goto error_add_memory;
 987         }
 988         move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
 989                                 align_start >> PAGE_SHIFT,
 990                                 align_size >> PAGE_SHIFT, NULL);
 991         mem_hotplug_done();
 992
 993         for (pfn = devmem->pfn_first; pfn < devmem->pfn_last; pfn++) {
 994                 struct page *page = pfn_to_page(pfn);
 995
 996                 page->pgmap = &devmem->pagemap;
 997         }
 998         return 0;
 999
1000 error_add_memory:
1001         untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
1002 error_radix:
1003         hmm_devmem_radix_release(devmem->resource);
1004 error:
1005         return ret;
1006 }
1007
1008 static int hmm_devmem_match(struct device *dev, void *data, void *match_data)
1009 {
1010         struct hmm_devmem *devmem = data;
1011
1012         return devmem->resource == match_data;
1013 }
1014
1015 static void hmm_devmem_pages_remove(struct hmm_devmem *devmem)
1016 {
1017         devres_release(devmem->device, &hmm_devmem_release,
1018                        &hmm_devmem_match, devmem->resource);
1019 }
1020
1021 /*
1022  * hmm_devmem_add() - hotplug ZONE_DEVICE memory for device memory
1023  *
1024  * @ops: memory event device driver callback (see struct hmm_devmem_ops)
1025  * @device: device struct to bind the resource too
1026  * @size: size in bytes of the device memory to add
1027  * Returns: pointer to new hmm_devmem struct ERR_PTR otherwise
1028  *
1029  * This function first finds an empty range of physical address big enough to
1030  * contain the new resource, and then hotplugs it as ZONE_DEVICE memory, which
1031  * in turn allocates struct pages. It does not do anything beyond that; all
1032  * events affecting the memory will go through the various callbacks provided
1033  * by hmm_devmem_ops struct.
1034  *
1035  * Device driver should call this function during device initialization and
1036  * is then responsible of memory management. HMM only provides helpers.
1037  */
1038 struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
1039                                   struct device *device,
1040                                   unsigned long size)
1041 {
1042         struct hmm_devmem *devmem;
1043         resource_size_t addr;
1044         int ret;
1045
1046         static_branch_enable(&device_private_key);
1047
1048         devmem = devres_alloc_node(&hmm_devmem_release, sizeof(*devmem),
1049                                    GFP_KERNEL, dev_to_node(device));
1050         if (!devmem)
1051                 return ERR_PTR(-ENOMEM);
1052
1053         init_completion(&devmem->completion);
1054         devmem->pfn_first = -1UL;
1055         devmem->pfn_last = -1UL;
1056         devmem->resource = NULL;
1057         devmem->device = device;
1058         devmem->ops = ops;
1059
1060         ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
1061                               0, GFP_KERNEL);
1062         if (ret)
1063                 goto error_percpu_ref;
1064
1065         ret = devm_add_action(device, hmm_devmem_ref_exit, &devmem->ref);
1066         if (ret)
1067                 goto error_devm_add_action;
1068
1069         size = ALIGN(size, PA_SECTION_SIZE);
1070         addr = min((unsigned long)iomem_resource.end,
1071                    (1UL << MAX_PHYSMEM_BITS) - 1);
1072         addr = addr - size + 1UL;
1073
1074         /*
1075          * FIXME add a new helper to quickly walk resource tree and find free
1076          * range
1077          *
1078          * FIXME what about ioport_resource resource ?
1079          */
1080         for (; addr > size && addr >= iomem_resource.start; addr -= size) {
1081                 ret = region_intersects(addr, size, 0, IORES_DESC_NONE);
1082                 if (ret != REGION_DISJOINT)
1083                         continue;
1084
1085                 devmem->resource = devm_request_mem_region(device, addr, size,
1086                                                            dev_name(device));
1087                 if (!devmem->resource) {
1088                         ret = -ENOMEM;
1089                         goto error_no_resource;
1090                 }
1091                 break;
1092         }
1093         if (!devmem->resource) {
1094                 ret = -ERANGE;
1095                 goto error_no_resource;
1096         }
1097
1098         devmem->resource->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY;
1099         devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
1100         devmem->pfn_last = devmem->pfn_first +
1101                            (resource_size(devmem->resource) >> PAGE_SHIFT);
1102
1103         ret = hmm_devmem_pages_create(devmem);
1104         if (ret)
1105                 goto error_pages;
1106
1107         devres_add(device, devmem);
1108
1109         ret = devm_add_action(device, hmm_devmem_ref_kill, &devmem->ref);
1110         if (ret) {
1111                 hmm_devmem_remove(devmem);
1112                 return ERR_PTR(ret);
1113         }
1114
1115         return devmem;
1116
1117 error_pages:
1118         devm_release_mem_region(device, devmem->resource->start,
1119                                 resource_size(devmem->resource));
1120 error_no_resource:
1121 error_devm_add_action:
1122         hmm_devmem_ref_kill(&devmem->ref);
1123         hmm_devmem_ref_exit(&devmem->ref);
1124 error_percpu_ref:
1125         devres_free(devmem);
1126         return ERR_PTR(ret);
1127 }
1128 EXPORT_SYMBOL(hmm_devmem_add);
1129
1130 struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
1131                                            struct device *device,
1132                                            struct resource *res)
1133 {
1134         struct hmm_devmem *devmem;
1135         int ret;
1136
1137         if (res->desc != IORES_DESC_DEVICE_PUBLIC_MEMORY)
1138                 return ERR_PTR(-EINVAL);
1139
1140         static_branch_enable(&device_private_key);
1141
1142         devmem = devres_alloc_node(&hmm_devmem_release, sizeof(*devmem),
1143                                    GFP_KERNEL, dev_to_node(device));
1144         if (!devmem)
1145                 return ERR_PTR(-ENOMEM);
1146
1147         init_completion(&devmem->completion);
1148         devmem->pfn_first = -1UL;
1149         devmem->pfn_last = -1UL;
1150         devmem->resource = res;
1151         devmem->device = device;
1152         devmem->ops = ops;
1153
1154         ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
1155                               0, GFP_KERNEL);
1156         if (ret)
1157                 goto error_percpu_ref;
1158
1159         ret = devm_add_action(device, hmm_devmem_ref_exit, &devmem->ref);
1160         if (ret)
1161                 goto error_devm_add_action;
1162
1163
1164         devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
1165         devmem->pfn_last = devmem->pfn_first +
1166                            (resource_size(devmem->resource) >> PAGE_SHIFT);
1167
1168         ret = hmm_devmem_pages_create(devmem);
1169         if (ret)
1170                 goto error_devm_add_action;
1171
1172         devres_add(device, devmem);
1173
1174         ret = devm_add_action(device, hmm_devmem_ref_kill, &devmem->ref);
1175         if (ret) {
1176                 hmm_devmem_remove(devmem);
1177                 return ERR_PTR(ret);
1178         }
1179
1180         return devmem;
1181
1182 error_devm_add_action:
1183         hmm_devmem_ref_kill(&devmem->ref);
1184         hmm_devmem_ref_exit(&devmem->ref);
1185 error_percpu_ref:
1186         devres_free(devmem);
1187         return ERR_PTR(ret);
1188 }
1189 EXPORT_SYMBOL(hmm_devmem_add_resource);
1190
1191 /*
1192  * hmm_devmem_remove() - remove device memory (kill and free ZONE_DEVICE)
1193  *
1194  * @devmem: hmm_devmem struct use to track and manage the ZONE_DEVICE memory
1195  *
1196  * This will hot-unplug memory that was hotplugged by hmm_devmem_add on behalf
1197  * of the device driver. It will free struct page and remove the resource that
1198  * reserved the physical address range for this device memory.
1199  */
1200 void hmm_devmem_remove(struct hmm_devmem *devmem)
1201 {
1202         resource_size_t start, size;
1203         struct device *device;
1204         bool cdm = false;
1205
1206         if (!devmem)
1207                 return;
1208
1209         device = devmem->device;
1210         start = devmem->resource->start;
1211         size = resource_size(devmem->resource);
1212
1213         cdm = devmem->resource->desc == IORES_DESC_DEVICE_PUBLIC_MEMORY;
1214         hmm_devmem_ref_kill(&devmem->ref);
1215         hmm_devmem_ref_exit(&devmem->ref);
1216         hmm_devmem_pages_remove(devmem);
1217
1218         if (!cdm)
1219                 devm_release_mem_region(device, start, size);
1220 }
1221 EXPORT_SYMBOL(hmm_devmem_remove);
1222
1223 /*
1224  * A device driver that wants to handle multiple devices memory through a
1225  * single fake device can use hmm_device to do so. This is purely a helper
1226  * and it is not needed to make use of any HMM functionality.
1227  */
1228 #define HMM_DEVICE_MAX 256
1229
1230 static DECLARE_BITMAP(hmm_device_mask, HMM_DEVICE_MAX);
1231 static DEFINE_SPINLOCK(hmm_device_lock);
1232 static struct class *hmm_device_class;
1233 static dev_t hmm_device_devt;
1234
1235 static void hmm_device_release(struct device *device)
1236 {
1237         struct hmm_device *hmm_device;
1238
1239         hmm_device = container_of(device, struct hmm_device, device);
1240         spin_lock(&hmm_device_lock);
1241         clear_bit(hmm_device->minor, hmm_device_mask);
1242         spin_unlock(&hmm_device_lock);
1243
1244         kfree(hmm_device);
1245 }
1246
1247 struct hmm_device *hmm_device_new(void *drvdata)
1248 {
1249         struct hmm_device *hmm_device;
1250
1251         hmm_device = kzalloc(sizeof(*hmm_device), GFP_KERNEL);
1252         if (!hmm_device)
1253                 return ERR_PTR(-ENOMEM);
1254
1255         spin_lock(&hmm_device_lock);
1256         hmm_device->minor = find_first_zero_bit(hmm_device_mask, HMM_DEVICE_MAX);
1257         if (hmm_device->minor >= HMM_DEVICE_MAX) {
1258                 spin_unlock(&hmm_device_lock);
1259                 kfree(hmm_device);
1260                 return ERR_PTR(-EBUSY);
1261         }
1262         set_bit(hmm_device->minor, hmm_device_mask);
1263         spin_unlock(&hmm_device_lock);
1264
1265         dev_set_name(&hmm_device->device, "hmm_device%d", hmm_device->minor);
1266         hmm_device->device.devt = MKDEV(MAJOR(hmm_device_devt),
1267                                         hmm_device->minor);
1268         hmm_device->device.release = hmm_device_release;
1269         dev_set_drvdata(&hmm_device->device, drvdata);
1270         hmm_device->device.class = hmm_device_class;
1271         device_initialize(&hmm_device->device);
1272
1273         return hmm_device;
1274 }
1275 EXPORT_SYMBOL(hmm_device_new);
1276
1277 void hmm_device_put(struct hmm_device *hmm_device)
1278 {
1279         put_device(&hmm_device->device);
1280 }
1281 EXPORT_SYMBOL(hmm_device_put);
1282
1283 static int __init hmm_init(void)
1284 {
1285         int ret;
1286
1287         ret = alloc_chrdev_region(&hmm_device_devt, 0,
1288                                   HMM_DEVICE_MAX,
1289                                   "hmm_device");
1290         if (ret)
1291                 return ret;
1292
1293         hmm_device_class = class_create(THIS_MODULE, "hmm_device");
1294         if (IS_ERR(hmm_device_class)) {
1295                 unregister_chrdev_region(hmm_device_devt, HMM_DEVICE_MAX);
1296                 return PTR_ERR(hmm_device_class);
1297         }
1298         return 0;
1299 }
1300
1301 device_initcall(hmm_init);
1302 #endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */